1. Field of the Invention
The present invention relates to a flexible tube for an endoscope and an endoscope equipped with the flexible tube.
2. Description of the Prior Art
In an endoscopic examination, a flexible insertion tube of an endoscope is inserted along the body cavity to a deep part of a patient such as the stomach, duodenum, small intestine, and large intestine. For this reason, the flexible insertion tube of the endoscope is provided with an outer cover to improve ease of the inserting operation (that is, flexibility), which reduces a burden on a patient. In addition, the outer cover prevents fluids such as body fluids from entering the interior of the endoscope. In the prior art, an elastic material such as urethane-based elastomer has been generally used as a constituent material of the outer cover of the flexible insertion tube (see Japanese Patent Publication No. Hei 7-110270 (page 1, right column, lines 2–8), for example).
In the meantime, since an endoscope is repeatedly used, it must be cleaned and disinfected after each use. However, the above-mentioned material which has been conventionally used has a problem in that heat resistance and chemical resistance thereof are poor. For this reason, repeated cleaning, sterilization and disinfection of the endoscope deteriorates the outer cover of the flexible insertion tube, and then the flexibility of the outer cover itself is lowered, which may result in a case that it becomes difficult to insert the flexible insertion tube into a tubular cavity. Further, in a case where such deterioration is severe, small cracks and the like will occur, and as a result, there is a case that the constituent material of the outer cover of the flexible insertion tube will peel off.